We experienced two cases of spontaneous rupture of the urinary bladder associated with radiation cystitis. Case 1 and Case 2 were a 45-year-old female and a 71-year-old female, respectively. Both of them were admitted to our hospital with complaints of high grade fever and severe lower abdominal pain. They had a past history of total hysterectomy followed by radiationtherapy more than10 years ago. The cystography and the subsequent computed tomography revealed spontaneous rupture of the urinary bladder. We performed the operationto repair the perforationsite with omentum covering. Case 1 had a good postoperative course with intermittent self-catheterization after removal of urethral catheter. However, she died of cerebral hemorrhage during hospitalization. Although case 2 needed an indwelling urethral catheter due to the difficulty of intermittent self-catheterization, she had no recurrence of rupture for six months after the operation. Inthis way, total hysterectomy followed by radiationtherapy seems to be a risk factor for the spontaneous rupture of the urinary bladder. When we see a patient with acute abdomen, who has a history of hysterectomy followed by radiation, rupture of the urinary bladder can be a differential diagnosis.